-iT\CK 
ANKEX 


CT 


RADIO  t  RAFT 

Booklet  No.  1 


Miidel    Illustrating    Arrangement    o1    Radio    Kfffi\  inu    Set. 


Handcraft   Projects  for  School  antl   Home  Shops 


RADIO     CRAFT 

(Radio  Booklet  No.   1) 

FRANK   I.  SOLAR 

Nortliorn  lliuh  Stiiool,  Detroit,  Michigan. 


Editor  of  "Tool  Craft, roys  and  Useful  Articles  a  Buy  Can   Make.' 

"Practical  Construction   Work   for  Home  and  School   Shops," 
"Bird   Housts   uf   Simplt-   Constiuction" 


The  liriice  I'lihlishing  Company, 
Milwaukee,  Wisconsin. 


Cupyiight  1S)22 
The  Bi-uce  Publishing  Company 
Printed  in  V.  S.  A. 


TABLE  OF  CONTENTS 

Radio  Sets  as  Manual  Trainin.u-  Prujects 7 

Eadio   Craft 9 

The   Aerial 13 

Tuning  Coil  No.  1 Ki 

Plate  of  Tuning  Coil  No.  1 IT 

Tuning  Coil  No.  2 18 

Plato  of  Tuning  Coil  No.  2 19 

Making  the  Condenser 20 

Plate  of  the  Condenser 21 

Making   a    Detector 22 

Plate  of  a  Detector 23 

Receiving  Transformer  or  Loose  Coupler 24 

Plate  of  Receiving  Transformer 2.t 

Hook  Ups  for  Coils  and  Coupler 2S 

Plate  of  Hook  Ups  and  Coupler 29 


2065680 


RADIO  SETS  AS  MANUAL  TRAINING  PROJECTS 


The  making:  of  toys,  boats,  bird  houses,  kites  and 
aeroplanes  have  all  been  accepted  in  turn  with  great 
enthusiasm  by  boys  in  manual  training  classes.  Noth- 
ing however,  like  the  Radio  Craze  has  ever  caused  the 
boys  to  beg  to  come  in  and  work,  the  girls  to  inquire  if 
it  would  be  possible  for  them  to  do  work,  and  fathers 
and  mothers,  to  come  to  our  shops  for  parts  and  infor- 
mation, for  setting  up  Radio  receiving  sets. 

Most  of  the  projects  made  in  our  shops  such  as  book 
racks,  etc.,  will  serve  the  purpose  if  H-inch  longer  or 
shorter  than  the  drawing.  This  is  not  true  with  the 
wireless  receiving  set,  which  requires  less  material  than 
the  usual  models,  but  each  part  must  be  a  certain  size 
to  make  the  next  part  work,  and  the  boy  appreciates 
the  meaning  of  real  accuracy.  It  also  instills  in  him  a 
desire  to  search  the  shelves  of  the  public  library  and  to 
study  books  on  this  subject.  It  makes  him  rack  his 
brain  to  figure  out  how  to  make  use  of  available  sci'ap 
material  to  take  the  place  of  parts  that  he  has  not  the 
money  to  purchase. 

The  crowning  feature,  however,  of  this  project  is 
that  when  finished  it  looks  so  different  from  the  usual 


article  the  boy  brings  home,  almost  like  an  infernal  ma- 
chine, that  the  whole  family  is  interested  to  the  extent 
of  offering  their  help  to  get  the  thing  rigged  up  for  a 
tryout.  This  is  so  different  from  the  usual  interest 
shown  when  the  boy's  work  is  brought  home,  which  con- 
sists of  an  expression — isn't  it  nice.  Then  the  article 
is  forgotten. 

The  boy  has  a  chance  to  tinker  with  the  elements  and 
with  many  different  kinds  of  materials.  This  is  the  best 
kind  of  education,  and  the  desire  for  learning  comes 
from  within.  It  is  a  chance  for  father  and  son  to  get 
together  and  work  on  a  problem  that  is  of  interest  to 
both. 

Let  the  boys  experiment,  for  it  will  drive  them  off 
the  streets  into  the  school  and  home  work  shops  where 
ever.v  boy  and  man  should  spend  some  of  his  spare  time. 
While  there  he  will  make  articles  that  will  not  only 
afford  pleasure  and  pastime  but  will  be  a  benefit  edu- 
cationall.v  to  the  household.     Let  the  good  work  go  on. 

F.  I.  S. 


RADIO  CRAFT 


lllustratiun    1.     Tunini.''  Coil.     See  page   Ifi. 


RADIO  CRAFT 


Radio  and  wireless  experinientins'  by  amateurs  in 
this  country  had  gotten  nicely  underway  about  the  time 
the  World  war  started.  Due  to  the  fact  that  war  de- 
partment reg'ulations  required  aerials  to  be  disman- 
tled, amateurs  had  to  lay  aside  their  equipment  for 
a  while.  However,  after  peace  was  declared  experi- 
menting' soon  became  popular  again.  After  the  special 
training  received  in  service  many  more  young  people 
were  interested  and  had  considerable  more  practical  and 
theoretical  knowledge  of  the  work  than  those  interested 
before  the  war. 

The  average  person  was  not  any  more  interested  in 
Radio,  than  in  any  other  new  feature  brought  to  his 
attention.  The  reason  for  this  was  that  most  broad- 
casting was  done  in  code,  and  it  is  a  considerable  task 
to  master  the  code  so  one  can  receive.  And  even  for 
those  who  could  receive,  the  information  gained,  was 
of  little  interest. 

When  different  agencies  began  broadcasting  music, 
entertainments,  lectures,  news,  etc.,  to  be  heard  by  the 
aid  of  the  radio-phone,  everyone  became  interested. 
And  today  we  have  thousands  of  people  all  over  the 
world  enjoying  entertainments  daily. 

There  are  no  laws  governing  the  use  of  receiving  sets 
and  the  handy  person  can  make  one  that  will  receive 
the   broadcasting   in    his   vicinity.      The   sending,   how- 


ever, requires  an  expensive  apparatus  and  also  a  license, 
the  obtaining  of  which  involves  certain  qualifications 
and  requirements.  This  is  of  little  concern  to  most 
people  as  they  are  content  to  listen  to  others  of  interest 
rather  than  spend  their  time  jamming  the  air. 

Almost  any  of  the  apparatus  used  for  broadcasting 
and  receiving  can  be  made  or  assembled  by  the  handy 
man,  boy  and  mechanic.  Although  material  required  is 
quite  expensive  for  the  larger  outfits,  the  average  ex- 
pert worker,  even  if  competent  to  make  a  set,  could 
not  afford  to  invest  a  great  amount  in  material.  Per- 
sons who  can  afford  to  will  no  doubt  buy  a  complete  set, 
and  even  if  they  were  capable  would  not  have  the  time 
to  make  their  own  sets.  There  are  thousands  of  people 
who  would  like  to  listen  in  on  the  programs  offered. 
They  would  like  to  make  their  own  outfits  and  can  do  so 
by  following  the  directions  given  in  the  following  pages. 

The  following  drawings  and  instructions  are  given  to 
be  used  by  the  handv  man  and  boy  in  the  home  and 
school  shops.  It  is  not  intended  to  give  any  technical 
discussion  in  this  description  but  to  show  by  drawings 
and  a  brief  explanation  how  to  set  up  a  receiving  outfit 
at  a  minimum  cost.  This  set  is  similar  to  many  that 
my  boys  have  already  made.  By  the  aid  of  such  sets 
they  are  receiving  gi-eat  enjoyment  listening  to  the  code 
and  the  wondei-ful  programs  they  are  able  to  get. 


10 


RADIO  CRAFT 


One  of  these  little  receiving  sets  will  be  worth  a 
great  deal  to  the  busy  mother  unable  to  leave  home 
evenings,  to  crippled  people  confined  to  their  beds  or 
chairs,  to  convalescents,  and  people  living  far  out  in 
the  country  and  at  resorts  in  the  summer  time. 

Do  not  be  misled  by  statements  that  for  a  dollar  or 
two  you  can  make  a  set  that  can  be  connected  to  your 
victrola  and  heard  all  over  the  house,  or  that  will  re- 
ceive concerts  broadcast  at  a  great  distance.  This  is 
not  true.  To  do  this  requires  a  set  composed  of  at  least 
the  following  equipment,  in  addition  to  the  receivers 
and  aerial :  a  rheostat,  amplifier  panel,  bulb,  grid  con- 
denser, grid  leak,  six  volt  (A)  battery  and  a  (B)  bat- 
tery.   An  outfit  of  this  kind  costs  $65  and  up. 

The  wireless  and  radio-phone  are  still  in  an  experi- 
mental stage  and  it  is  advisable  to  investigate  and  pick 
a  reliable  standard  set  rather  than  to  invest  consider- 
able money  in  inferior  wireless  apparatus.  In  a  short 
time  marvelous  new  equipment  will  be  on  the  market 
and  an  outfit  may  be  hooked  to  the  electric  circuit  and 
even  the  ordinary  telephone  may  be  used  to  receive 
broadcasting.  It  would  be  well  woith  while  for  those 
interested  in  this  new  venture  to  make  a  home  made 
receiving-  set  first  and  do  a  little  experimenting  until 
they  decide  on  the  larger  set  they  want.  Most  of  this 
beginning  apparatus  can  later  be  hooked  in  with  the 
more  expensive  set. 


lllustratiun 


.\    I'lirlabk-    Hume    .\lLide    Outfit. 


RADIO  CRAFT 


11 


Illustration  3.     A   Pocket  Outfit. 


Illustration   4.      A    Tuning   Coil   and  the   Boy   \\'ho    Made   It. 


12 


RADIO  CRAFT 


Illustration    5.      Home    Mr.de    Loose    Couplers,    Condenser.    Detector    .thH    Coil    Wound    on    Nails. 


THE    AERIAL 


The  first  thiiiK  to  be  cun.sidered  when  installing  a 
receiving  set  is  the  aerial.  Of  course  it  is  possible  to 
get  results  from  your  bed  spring's,  the  eaves  trough,  a 
metal  railing  and  many  other  things,  but  natuially  a 
specially  erected  aer'al  is  the  most  satisfactory. 

A  loop  aerial  may  be  erected  indoors.  It  may  be 
stretched  in  the  attic  or  any  room.  Some  have  .strung' 
the  aerial  across  the  room  from  the  picture  molding  on 
one  side  to  the  molding  on  the  other.  A  row  of  picture 
hooks  or  sci-ew  eyes  will  do  to  support  it.  While  it  is  up 
out  of  the  way  it  is  not  very  convenient  on  house  clean- 
ing day.  Two  coat  hangers  hunLi'  at  either  end  of  the 
room  will  make  good  stretchers. 

Sound  waves  travel  through  the  ether  and  are  caught 
by  the  antenna  of  the  aerial,  which  is  the  part  sus- 
pended between  the  stretchers. 

Almost  any  length  of  aerial  at  any  height  from  the 
ground  will  give  results  for  receiving  from  a  short 
distance.  The  higher  from  the  .uround  and  the  longer 
the  antenna  the  better. 

Excellent  results  will  be  obtained  by  a  7.5  to  1.50  f<iot 
aerial  placed  from  30  to  .50  feet  from  the  ground.  The 
antenna  should  be  allowed  to  sag  a  little  so  it  can  blow 
in  the  breeze  and  thus  shake  off  the  snow  and  ice  which 
might  collect  and  break  it  if  strung  tight. 


For  small  sets  to  receive  from  a  short  distance  any 
kind  of  wire  will  do,  either  bare  or  insulated.  The  best 
wire  to  use  is  No.  14  copper  or  aluminum  (bare).  For 
guy  wii-es  use  No.  10  or  12  telephone  wire. 

The  laws  require  that  amateurs  send  on  not  over  a 
200  meter  wave  length.  The  four  wire  aerial,  illus- 
trated in  Fig.  1  is  7.5  or  80  feet  long,  and  is  about  right 
for  sending  this  length  wave.  The  masts  which  are 
fastened  and  braced  to  the  peaks  of  the  roof  may  be 
any  length.  The  stretchers  should  be  about  nme  feet 
long  and  the  wires  equally  spaced.  At  the  free  end  M 
the  wires  may  or  may  not  be  connected  with  each  other. 
The  other  end  N,  from  which  the  lead  in  is  taken,  should 
have  each  wire  of  the  antenna  connected  to  one  that 
leads  in  to  the  instrument. 

Fig.  2  shows  a  short  one  wire  aerial  having  the 
masts  fastened  to  the  front  and  back  of  the  house.  Fig. 
3  shows  bicycle  rims  or  barrel  hoops  used,  where  it  is 
not  convenient  to  get  long  stretchers. 

Fig.  4  is  an  aerial  stretched  from  a  house  to  a  garage 
and  Fig.  5  shows  one  wired  to  chimneys  on  an  apart- 
ment building. 

Fig.  6  illustrates,  at  A  and  B,  how  ordinary  porce- 
lain cleats  or  glass  pony  insulators  are  used  where  the 
antenna  is  connected  to  the  spreaders.  The  one  wire 
aerial  insulated,  as  shown  in  Fig.  7,  is  made  as  long  as 


13 


14 


RADIO  CRAFT 


possibk'  and  is  the  easiest  to  erect  and  will  j;ivo  good 
results.  The  loose  ends  can  be  attached  to  screw  eyes 
screwed  at  any  convenient  place  from  the  house  to  the 
barn,  a  tree,  post  or  the  garage. 

A  lightning  switch,  if  large  enough  to  be  of  any 
account,  is  rather  expensive.  A  drawing  for  one  that 
can  be  made  from  Vg-inch  or  thicker  sheet  copper,  and 
a  cement  base  is  given  in  lUus.  1.  A  box  of  wood  can 
be  made  into  which  to  pour  the  cement.     Pegs  should 


be  insei'ted  in  the  cement  while  soft  and  jiulled  out 
after  it  has  hardened  to  make  holes  for  fastening  to 
the  window  sill.  The  posts  can  be  held  in  place  by  a 
piece  of  stick  suspended  over  the  top  of  the  box  while 
the  cement  is  hardening.  To  conform  to  wiring  regu- 
lations it  will  be  necessary  to  place  a  plate  of  composi- 
tion material  beneath  the  cement. 

A  porcelain,  glass  or  rubber  tube  may  be  used  to 
insulate  the  lead  in  wire  where  it  passes  through  the 
sash. 


RADIO  CRAFT 


15 


RADIO   AERIAL 


LiaHTNiNG  Switch 


Fia  3 


,  Bicycle  Rims 

OR 

Barrel  Hoops 


ferf 


O^ 


Details  of   Aerial   and   Suggestive   Methods   »»f    Mounting. 


TUNINC;  (OIL  No.  1 


The  radio  waves  are  sent  out  in  different  lengths  by 
different  broadcastinj;:  stations.  The  ones  you  wish  to 
receive  must  be  tuned  in  so  you  can  receive  them.  This 
is  accomplished  by  moving  the  sliders  on  the  sliding 
rods. 

This  outfit  is  made  up  complete  so  that  by  connecting 
your  aerial  at  A  your  ground  at  B  and  your  phones  at 
G  and  H  you  are  ready  to  tune  in  and  receive. 

The  coil  can  be  wound  on  either  a  cardboard  tube  or 
a  solid  piece  of  wood.  If  w-ood  is  used  be  sure  it  is 
well  seasoned  or  it  will  shrink  and  your  wire  will  hang 
loose  on  it. 

The  first  thing  to  make  is  the  coil.  For  this  get  a 
rolling  pin  and  saw  off  the  handles.  To  hold  one-half 
pound  of  wire  it  should  be  2%  inches  in  diameter  and 
10^4  inches  long.  Make  a  groove  with  the  marking  gauge 
iV.-inch  from  one  end.  Drive  a  brad  alongside  the 
groove  and  then  give  that  end  of  the  pin  a  coat  of 
shellac.  We  are  going  to  make  the  coil  by  winding  No. 
22  enameled  copper  wire  around  the  pin.  Twist  the  wire 
around  the  nail  twice,  about  6  inches  from  the  end  of 
the  wire.  This  end  is  left  for  making  a  connection. 
Now  wind  around  the  pin,  the  first  time  around  running 
the  wire  in  the  groove.  This  is  done  while  the  shellac 
is  wet  and  it  will  help  hold  the  wire  in  place  when  it 


dries.  11'  you  shellac  as  you  wind,  it  will  not  be  neces- 
sary to  get  the  shellac  on  your  hands.  When  you  have 
reached  the  other  end  of  the  pin  drive  another  brad  and 
fasten  the  wire  as  before  but  the  six  inches  at  this 
end  should  be  wound  around  a  pencil  making  a  pig 
tail.     This  end  has  no  connection. 


lUustration   6.     Winding  a  Coil. 


16 


RADIO   CRAFT 


17 


M-  Ca  T  \NhI5KER 

N-  Crystal  cup 
O-  TiGiiTNiNc  Screw 

P' CRYSTAL 


u 


-/2- 


TUNINGCOIL  No. I. 


■^PouND  No  SB  Enamel  £0 
Copper  Wire-  Bare 


Rolling  Pin 


Slider 


L  J  L  J 


-iir 


:ir.., 


^^rFI 


Base 

Plan  For  v^/ring 

RIAL  iCoNDEHSER    4  Sliders 

Z  Detector       SPisTail 

i  Slider  Roos 
^       3     4    c 


Details  of   Tuning   Coil   No.  1. 


18 


RADIO  CRAFT 


Lay  the  coil  aside  and  niakp  the  ends.  Fasten  them  to 
the  coil  with  screws  about  IV2  inches  from  the  top  of  the 
end  pieces.  Next  make  the  base  and  fasten  to  the  end 
pieces  and  then  the  legs  and  fasten  them  to  the  base. 

Now  if  you  wish  to  purchase  your  parts,  buy  two 
A-inch  square  brass  slider  rods  and  sliders  to  fit.  Also 
a  condenser  and  a  detector.  If  you  wish  to  make  all 
parts,  information  for  makinp  them  can  be  had  from 
following  drawings. 

Your  connections  can  be  made  at  the  end  of  the 
slider  rods  by  fastening  the  wires  under  the  brass  round 
head  screws  that  hold  the  slider  rods  in  place. 

Now  we  shall  wire  the  tuning  coil.  Bore  holes  for  the 
binding  posts  at  A  and  B  and  also  for  the  wires  that 
are  connected  to  them.  Connect  straight  wire  left  at 
the  end  of  the  coil  to  A,  after  running  it  through  the 


hole  in  the  end  piece  and  scraping  off  the  insulation  to 
make  a  good  connection.  Connect  wire  to  the  end  of 
the  slider  rod  at  C,  run  through  the  hole  in  the  base, 
across  underneath  the  base,  up  through  the  hole  at  the 
opposite  end  and  through  the  one  in  the  end  and  con- 
nect to  B.  Connect  a  wire  to  post  G  on  the  condenser 
and  run  through  holes  to  post  B.  Connect  H  on  the 
condenser  to  F  on  the  detector.  Connect  E  the  crystal 
cup  screw  with  slider  rod  D. 

The  cat  whisker  of  the  detector  is  lettered  M,  the 
crystal  P,  the  crystal  cup  N  and  the  set  screw  O. 

The  wood  work  on  this  instrument  should  be  stained 
and  shellaced  or  varnished  to  add  to  its  appearance. 

Scrape  the  enamel  from  the  wire  where  the  points  of 
the  sliders  touch.  Be  sure  all  connections  are  well  made 
and  no  insulation  is  left  between  them. 

This  instrument  is  ready  for  use. 


TUNING  COIL  NO.  2 


This  coil  has  the  same  capacity  as  coil  No.  1  but  can 
be  made  much  cheaper  as  the  wire  is  the  only  thing  that 
need  be  purchased  . 

An  ordinary  oat  meal  or  cereal  box  is  used  in  place 
of  the  rolling  pin  on  which  to  wind  the  coil.  Be  sure 
that  the  cereal  box  is  dry  and  give  it  a  coat  of  shellac 
to  stiffen  it.  If  the  coil  is  wound  on  a  damp  box,  the 
wire  will  come  loose  when  the  box  dries  out. 


Begin  work  on  this  instrument  by  making  and  wind- 
ing the  coil.  The  top  and  bottom  of  the  box  are  re- 
moved and  wooden  discs  are  tacked  in  the  ends  of  the 
tube.  The  discs  can  be  sawed  to  shape  with  a  coping 
saw. 

Make  the  wood  frame  for  holding  the  coil.  This  needs 
no  further  explanation,  as  the  construction  and  sizes 
of  different  parts  can  be  learned  from  the  drawing. 


RADIO  CRAFT 


19 


Tuning  coil  No.i. 

This  coil  isCapable  Of  receiving  a 5 
WELL  A3  No.i  But  As  No  rods. Sliders  Or 
Posts  Are  used  only  viire  need  Be  Purchased 


No  14  COPPER  WIRE 

r-TA  K£     Two 


Details   for   Making  Tuning   Coil   No. 


20 


RADIO  CRAFT 


The  sliders  are  made  of  wire  and  slide  lui  tlie  wooden 
frames  connected  to  the  uprights  at  the  ends.  This 
saves  the  expense  of  slider  rods,  etc. 

The  windin,?:  of  the  coil  and  the  wirin."-  of  this  instru- 
ment are  the  same  as  explained  for  Coil  No.  1. 

Screw  eyes  and  rubber  bands  should  be  adjusted,  as 
shown  on  the  drawing,  at  both  ends  of  the  instrument. 
The  rubber  bands  hold  the  points  of  the  sliders  in 
close  contact  to  the  coil.  Scrape  the  insulation  where 
the  sliders  touch  the  coil,  as  instructed  for  Coil  No.  1. 

The  instrument  should  be  stained  and  shellaced  or 
varnished  to  add  to  its  appearance. 

Instead  of  hooking  to  the  end  of  the  slider  rod,  as 
instructed  for  Coil  No.  1,  on  this  coil  hook  to  the  eye  in 
the  slider  itself. 

MAKIN(;   THE  CONDENSER 

It  is  the  practice  in  connecting  up  receiving  sets  to 
use  a  small  fixed  condenser  across  the  telephone  ter- 
minals. The  condenser  acts  as  a  stopping  condenser. 
In  small  set  hook  ups  some  are  able  to  get  results  with- 
out the  condenser. 

Materials   needed   for  the  condenser  are   as   follows: 

1  Piece  of  wood,  %  x^Vi  x  6  inches. 

2  Pieces  of  Cardboard,  3V4  x5%  inches. 

10  Sheets  of  tin  foil,  3x4y2   inches. 

11  Pieces  of  waxed  paper,  .3'4  x4  inches. 
2  Binding  posts. 

4  Pieces  of  thin  sheet  brass. 
Some  vaseline. 


Begin  making  the  condenser  by  cutting  11  pieces  ol 
waxed  paper  according  to  pattern  C. 

Next  cut  ten  pieces  of  tin  foil  according  to  pattern  B 
and  two  pieces  of  cardboard  like  pattern  A. 

Place  a  piece  of  cardboard  A  on  the  table  and  with 
the  fingers  spread  on  the  upper  face  a  thin  covering 
of  vaseline,  .just  enough  to  hold  the  first  sheet  of  waxed 
paper  in  place.  Lay  the  first  sheet  of  waxed  paper  C. 
on  the  cardboard  and  grease  the  upper  side  as  you  did 
the  cardboard.  Now  place  the  first  sheet  of  tin  foil  on 
the  waxed  paper,  with  the  %"  x  %"  projection,  ex- 
tending at  one  end.  Continue  piling  up  the  pieces  as 
indicated  on  the  drawing.  The  next  piece  of  tin  foil 
should  have  %"  x  %"  projection,  extending  at  the  oppo- 
site end.  Continue  greasing  and  piling  the  parts,  being 
sure  to  alternate  the  projection  on  the  tin   foil   sheets. 

Cut  the  thin  sheet  brass  washers  and  put  in  place. 

iVIake  the  wooden  base  and  bore  holes  for  the  binding 
posts. 

Place  the  condenser  on  the  wood,  after  it  has  been 
pressed  together  tightly.  Locate  and  bore  holes.  As- 
semble according  to  the  drawing  ready  for  connecting 
to  the  set. 

If  desired  the  condenser  may  be  connected  directly 
to  the  base  of  the  tuning  coil  instead  of  attaching  to  the 
wooden  base. 

In  the  corner  of  the  drawing  will  be  found  pictures 
of  commercial  condensers,  that  can  be  purchased  for 
from  30c  to  $1,  depending  on  the  workmanship. 


RAniO  CRAFT 


21 


4      A__ 

B    -■   :-, 
B    - 
B  —  = 

fl  — — 


c 

VJaxed  Paper 
Bread  Wrapper 


'^ 


Condenser 


Nut  ^^, 


t 3" 


Dt-tails  uf   a    Hume   Made   L'undenser. 


MAKING   A    DETECTOR 


The  sound  waves  as  they  are  eauR-ht  by  the  antenna 
are  not  of  a  desirable  type  of  current.  They  must  be 
changed  to  the  suitable  type  and  this  is  done  by  the 
detector. 

The  materials  used  for  the  commercial  product  con- 
sist of  a  wooden  base,  two  binding  posts,  a  crystal  cup 
and  a  part  called  a  cat  whisker,  which  is  nothing  more 
than  a  pig  tail  made  of  bronze  spring  \vire.  The  pig 
tail  is  made  by  winding  the  wire  around  a  finishing 
nail. 

The  crystal  is  nothing  more  than  lead  sulphite  and 
may  be  called  galena,  carborundum,  silicon,  etc.  This 
mineral  must  be  chipped  off  to  make  a  bright  surface 
and  a  good  contact  with  the  cat  whisker.  Dust  soon 
gathers  on  the  surface  of  the  crystal.  This  can  be  pre- 
vented by  covering  the  whole  detector  with  a  large 
drinking  goblet  or  wooden  box. 

Practically  every  home  made  detector  is  made  in  a 
different  way  and  of  different  materials.  The  reason 
for  this  is  that  there  are  only  two  essential  points; 
first  some  means  of  holding  the  cat  whisker  so  it  can  be 
moved  about  and  adjusted  on  the  crystal;  and  second 
some  means  of  holding  the  crystal  tightly. 

The  detector  can  be  set  up  on  a  special  base  or  on 
the  base  of  the  tuning  coil. 


For  Type  1  get  a  piece  of  wood  %"  x  214"  x  4I/2", 
an  old  cuff  or  suspender  clip,  a  piece  of  sheet  brass,  five 
round  head  bi'ass  screws  and  a  piece  of  fine  brass  or 
bronze  spring  wire.  Bend  the  clip  and  brass  strip  to 
form,  as  indicated  on  the  drawing,  and  drill  holes  for 
the  screws.  If  the  hole  for  the  cat  whisker  screw  is 
made  smaller  than  the  size  of  the  screw  the  screw  when 
forced  through  the  hole  will  tap  out  the  hole.  Assemble 
the  parts,  solder  the  cat  whisker  to  the  screw  and  a  wing- 
in  the  slot  in  the  head  of  the  screw.  Insert  the  crystal 
in  clip,  and  tlii'  detector  is  ready  fur  business. 

Type  2  is  made  similar  to  Type  1,  except  that  all 
parts  may  be  purchased  and  only  the  assembling  is  to 
be  done.  The  conni'ctions  in  this  case  are  made  betvvi'en 
the  nuts  at  J. 

The  adjustment  and  sensitiveness  of  the  detector 
are  responsible  for  the  success  of  your  set.  So  it  is 
quite  important  that  you  buy  a  good  piece  of  tested 
mineral  or  crystal. 

Be  sure  when  making  connections  antl  before  sol- 
dering any  joints  that  all  parts  are  well  scraped. 
Not  scraping  off  the  insulation  is  often  the  cause  of 
poor  results. 


22 


RADIO  CRAFT 


23 


DETECTOR 


Type  / 


Type  2 


CUFF  CL  IP 


V 

B 

^ 

^ 

J 

i 

^-^ 


4  - 


F 


tniflO 


Commercial  Type 


F 


£ 


.J^ 


/^ 


Boy  OF  GALENA 


/^-  Wood 

B-  No  36  Bra  35  Spring  Wipe 

C-  Galena 

D- Sheet  Brass 

E- Heavy  Copper  vjire 

f- Bin  DING  Post 

G-Galena  Cup 

h-Set  Screw 

J-  Brass  Stove Bol  t  ^Nuts 


Details    for    the    Conbtrucliun    of    a    Detector. 


RECEIVING  TRANSFORMER  OR  LOOSE  COUPLER 


A  loose  coupler  is  more  difficult  to  make  than  a  tuning 
coil  but  it  will  give  better  results. 

It  is  for  the  same  purpose  as  the  coil,  i.  e.,  to  tunc 
in  the  sound  waves. 

With  this  coupler,  a  good  detector,  a  sensitive  piece 
of  galena,  a  pair  of  2,000  ohm  receivers,  100  feet  of 
copper  antenna  well  insulated  suspended  on  an  aerial 
50  feet  from  the  ground  an  operator  should  be  able  to 
receive  from  200  to  300  miles. 

The  coupler  is  composed  of  two  tubes  both  wounil 
with  wire,  one  sliding  inside  of  the  other.  The  larger 
tube  is  called  the  primary  and  the  smaller  the  secon- 
dary. The  primary  is  set  to  the  wave  length  by  adjust- 
ing the  top  slider.  Then  the  switch  on  the  secondary  and 
the  coupler  (drawing  the  secondary  in  and  out  on  the 
rods)  are  manipulated  until  the  loudest  sound  is  heard. 

If  you  do  not  possess  many  tools  and  it  would  be 
difficult  for  you  to  make  the  box  it  need  not  all  be  made. 
The  only  parts  needed  are  the  bottom  and  the  two  ends. 

For  the  tubes  get  an  oatmeal  or  other  cereal  box  for 
the  primai-y  and  a  salt  box  for  the  secondary.  Be  sure 
they  are  dry  before  winding  the  wire  on  them,  so  they 
will  not  dry  out  and  shrink  after  being  wound.  It  will 
stiffen  the  cardboard  to  shellac  it  well  before  using. 


With  a  coping  saw,  cut  the  opening  in  the  front  piece 
and  then  make  %"  discs  according  to  the  drawing  to  fit 
the  back  of  the  primary  and  both  ends  of  the  secondary, 
also  a  Vi"  disc  to  fasten  to  the  front  of  the  secondary. 

Get  a  w."  sliding  curtain  rod,  that  is  one  that  has  a 
tin  tube  in  which  the  solid  rod  slides.  Cut  off  two  pieces 
of  each  tube  and  rod  the  length  of  the  box.  The  tubes 
are  to  be  inserted  in  the  ends  of  the  secondary  and  the 
solid  rods  are  to  be  filed  square  and  to  a  point  and 
driven  in  holes  throu.;h  the  disc  in  the  back  of  the 
primary  and  into  the  back  of  the  box. 

Wind  the  prnnary  with  No.  24  cotton  covered  copper 
wire  and  when  finished  give  it  a  good  coat  of  shellac. 
It  will  take  about  one  quarter  of  a  pound.  Start  Vu" 
from  the  end  of  the  box.  Fasten  the  ends  by  punching 
small  holes  in  the  cereal  box  and  threading  the  end  of 
the  wire  into  the  box.  The  wire  at  the  back  end  should 
be  twisted  so  it  will  not  come  loose;  but  the  one  at  the 
front  end  should  be  left  quite  long,  as  it  is  to  be 
threaded  back  through  the  box  and  out  at  the  back  end 
where  it  is  fastened  to  the  binding  post  (X). 

When  the  primary  is  wound  it  should  be  tacked  with 
•■■"  brads  to  the  disc  at  the  back  and  to  the  circumfer- 
ence of  the  hole  cut  in  the  front  piece. 


24 


RADIO   CRAFT 


25 


Receiving  Transformer 

OR 

LOOSE  COUPLER 


SLIDING  CURTA<.\ 
ROD  AND    TUBE 


Details,   for  Makinu   a   Loo!>f  Coupler   and   Picture  of  Commercial   Type. 


26 


RADIO   CRAFT 


Purchase  or  make  a  slider,  and  also  get  a  i',-. "  slider 
rod  6^4"  long.  Fasten  the  rod  to  the  top  of  the  box  as 
indicated  and  connect  it  to  a  binding:  post  at  Z  with  a 
piece  of  insulated  wire  having  one  end  turned  under 
the  screw  at  Y. 

Now  we  shall  wind  the  secondary.  For  the  secondary 
we  need  about  one  quarter  pound  of  No.  30  silk  covered 
copper  wire,  a  rotary  lever  switch,  twelve  V*"  taps  or 
brass  headed  tacks  and  two  pieces  of  flexible  copper 
wire,  each  18"  lonir.  Silk  covered  electric  light  cord 
will  do  for  the  flexible  wire. 

Along  the  top  of  the  secondary,  divide  off'  the  space 
into  twelve  parts  and  at  each  division  punch  a  hole 
with  a  darning  needle.  Start  about  '^  inch  from 
the  end  to  make  the  divisions  and  end  about  th's 
distance  from  the  other  end.  Start  winding  by  thread- 
ing the  end  of  the  wire  through  the  first  hole  No.  1  at 
the  back  end  of  the  secondary.  Scrape  the  end  of  this 
wire  and  solder  it  to  one  end  of  one  of  the  pieces  of 
flexible  wire.  This  flexible  wire  is  to  be  threaded  out  of 
the  tube  through  hole  A  when  this  front  disc  is  finally 
fastened  in  place.  Start  now  and  wind  until  the  wire 
comes  to  the  center  of  the  next  hole.  {Do  not  cut  the 
wire  but  make  a  long  loop  tliut  irill  reach  two  inches 
out  of  the  front  of  the  tube)  thread  through  hole  No.  2. 


Contimic  to  wind  and  loop  through  holes  until  hole  12 
is  reached. 

Now  scratch  the  insulation  off"  of  the  wire  at  the  end 
of  each  loop  and  fasten  under  the  nut  of  the  taps  or 
solder  to  the  ends  of  brass-headed  tacks,  if  they  are  used 
for  taps.  Of  course  the  location  of  the  taps  must  be 
spaced  off  on  the  front  disk  of  the  secondary  and  holes 
bored  for  them,  and  also  for  the  switch.  Fasten  one 
end  of  the  other  flexible  wire  to  the  switch  post  inside 
the  tube  and  thread  out  with  the  other  flexible  wii-e 
through  hole  A.  Now  place  the  front  head  in  the  tube 
and  fasten  with  '4"  round  head  screws  so  it  can  be 
easily  removed  if  repairs  have  to  be  made  to  the  wires 
inside  of  the  tube. 

Scratch  the  insulation  off  the  wire  coil  on  tlic  pri- 
mary, directly  under  the  slider  rod  so  that  the  slider 
will  make  a  good  contact.  The  tongue  of  the  slider  will 
have  to  be  bent  no  doubt  to  the  proper  shape. 

For  the  hook  up  look  at  the  diagram  on  the  sheet  of 
hook  ups. 

Z  is  connected  to  the  aerial,  X  is  connected  to  the 
ground,  the  switch  of  the  secondary  to  the  condenser 
and  the  other  flexible  wire  from  hole  1  to  the  detector. 

To  improve  the  looks  of  your  instrument  stain  ma- 
hogany, varnish  and  rub  down  or  enamel  it  black. 


RADIO  CRAFT 


27 


Illustration    7.      Kadio  Apparatus   Made  by   Boys   Under    the    Author's    Direction   and    Successfully    Used. 


HOOK   UPS  FOR  COILS  AND  COUPLER 


The  term  hook  up  is  one  used  commonly  by  radio 
operators  and  means  the  method  of  wiring  the  pieces 
of  apparatus  together  to  mal<e  up  a  set. 

There  are  many  different  ways  of  wiring  or  connect- 
ing the  instruments  together  to  get  results  and  little 
difference  can  be  noticed  by  the  different  methods.  So 
if  by  chance  you  connect  your  set  differently  from  the 
diagrams  given  on  the  drawini;-  you  may  get  just  as 
good   results. 

We  shall  trace  the  hook  up  in  Fig.  1.  The  aerial  A  is 
connected  to  the  lightning  switch  at  the  center  post  B 
by  the  lead  in  wire,  X.  If  you  cannot  afford  a  lightning 
switch,  arrange  your  lead-in  wire  so  it  can  be  discon- 
nected from  the  post  B,  fastened  to  an  iron  weight  and 
swung  at  least  6  feet  away  from  the  house  to  the 
ground  when  not  in  use.  If  you  have  a  switch  connect 
the  ground  post  C  by  a  piece  of  No.  (!  wire  to  a  piece 
of  gas  pipe,  driven  into  the  ground.  When  not  in  use 
throw  your  switch  to  this  post  C. 

Connect  post  D  with  the  end  of  your  coil  wire  E. 
The  other  end  of  your  coil  wire  is  pig  tailed  and  has 
no  connection,  as  F.  Connect  H  to  your  water  faucet, 
a  radiator,  or  a  wire  run  to  a  pipe  driven  in  the  ground 
at  G.  Also  connect  one  post  of  your  condenser  .1  to 
your  ground  wire  G.  Connect  the  other  post  E  of  your 
condenser  to  post  L  of  your  detector  N.     Now  connect 


post  N  of  your  detector  to  post  O  the  end  of  the  other 
slider  rod  and  your  circuit  is  made. 

The  terminal  of  your  receivers  should  be  hooked  to 
the  binding  posts  at  K  and  J  on  the  condenser. 

Receivers  are  made  in  different  types.  A  commonly 
used  kind  is  the  ordinary  telephone  receiver  which  is 
about  75  or  80  ohms.  This  type  is  not  very  satisfactory 
because  it  must  be  held  by  the  hand  while  receiving. 
The  amateur  one-part  head  piece,  which  is  also  about 
7.')  ohms,  just  brings  the  message  to  one  ear  and  allows 
surrounding  sounds  to  go  to  the  other.  The  two  part 
head  set  of  from  2,000  to  3,000  ohms  is  very  satisfac- 
tory. A  2,000  ohm  head  piece  means  that  each  part  is 
a  1,000  ohm  unit. 

Fig.  2  shows  another  hook  up  for  the  tuning  coil 
and  can  be  easily  traced  after  reading  the  description 
for  Fig.  1. 

Fig.  o  is  a  book  u|)  foi-  the  loose  coupicf.  The 
aerial  in  this  case  is  connected  with  the  slidi  r  II.  The 
front  end  of  the  pi'imarv  wire  P  is  connected  to  ground 
G.  The  switch  Q  is  connected  with  flexible  wire  to  the 
post  R  of  the  condenser  I.  The  post  S  of  condenser  is 
connected  to  post  T  of  detector.  The  post  U  of  the  de- 
tector is  connected  with  flexible  wire  fastened  to  the 
end  of  the  wire  at  the  back  end  of  the  secondary  \V. 
Y   is  the  primary. 


28 


IIADIO  CRAFT 


29 


Aic«, 


HOOK   UPS  FOR  COILS  AND  COUPLER 


Fig.  I 


Slid£R 


I g =  ffoo 


na.  3. 


Coil 


1^ 


I?      ^ 


Fiat- 


A -AERIAL 

X-  Lead  In 
G-Grouno 
M'  Detector 
I  -  Condenser 
Y'  Primary 
\N-  Secondary 
Q^  Switch 


Head  Set  Receivers 


Diagrams   lur    Hook   Ups 


30 


RADIO  CliAFT 


Illustration    8. 
Even   the   Doll    May  Share  the  Evening's   Broadcastinjf. 


Illustration    9. 
Making:   Work   a    Plt-asuri'   with   the   Radiophone. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 

Los  Angeles 
This  book  is  DUE  on  the  last  date  stamped  below. 


HEPDID-UW: 

NOV  2  4 1986 


B     000  003  233     4 


'«» 


I 


II 


fll! 


